The Brewers will get three prospects in return. The best of the three is shortstop Jean Segura, who has a nice tools package and a decent performance record, albeit with some injury concerns. He projects as a long-term part of the Brewers' middle infield, be it at short or second base. The other two players are both pitchers. John Hellweg is a tall righty who throws hard but doesn't know where the ball's going. He has star potential, but is a very risky pickup. Ariel Pena is shorter than Hellweg and doesn't throw as hard, but his stuff is still pretty good, and unlike Hellweg, he's taken a step forward with his command this year. On the whole, I think the package represents solid value for a couple months' worth of Greinke, who wasn't likely to re-sign with Milwaukee this offseason.
The move probably also drives a stake into the heart of the recent rumors about the Angels trading for Kevin Correia, as Jerry Dipoto has been quoted as saying that the Greinke trade "in all likelihood will be all we do" for the remainder of the pre-deadline period.